Ratio of the left and right side of the dispersion relation Eq. (36). The method to extract k_h/k from the simulation is described in the text. A ratio of unity corresponds to a perfect match and is reflected by white regions. A red color indicates a too large value of k_h/k and correspondingly the ratio is too small in blue regions. The white line is the BVF. For frequencies below the yellow line, IGWs are expected to be damped by thermal diffusion. Below the magenta line, the radial wavelength is resolved by less than 10 grid cells. The left column zooms into the low frequency region of the corresponding full plane on the right. The frequency given in the white boxes denotes the value of f_max which sets the scale of the corresponding x-axis.